Epidemiologic studies of temporal and geographic variation in asthma morbidity have identified asthma as an important public health concern. Knowledge gained from these studies has resulted in intense focus on this condition by agencies such as the National Institutes of Health and the World Health Organization. In this report, studies of recent asthma trends and patterns are explored. These studies show increases in US prevalence through 1994. Data on measures of morbidity show complex longitudinal patterns but are notable for large differences in emergency department services and hospitalizations by age and race. Very recent trends for US asthma mortality suggest widening of an existing racial gap. Limited comparisons are possible between these US trends and international trends but do suggest that US increases in prevalence and mortality rates may reflect world-wide patterns. Also, within the US, it is clear that geographic variation exists in asthma prevalence, morbidity, and mortality rates. Changes in certain environmental risk factors and exposures may contribute to recent trends, but little information is available relating specific risk factors to either longitudinal asthma trends, geographic variability, or high-risk populations.